# 1 (Test request)

The **`1` (Test Request)** message checks the connectivity and responsiveness of a counterparty during a FIX session.

It is sent by one party to the other, and the recipient is expected to respond promptly with a [**`0` (Heartbeat)**](/docs/guides/exchange-fix-api/trading-fix-api/supported-fix-messages/fix-session-level-messages/message-0-heartbeat) message with the same **112** `TestReqID`, indicating that the communication link is operational.

| Tag       | Name          | Type       | Required                                   | Description                                                       |
| --------- | ------------- | ---------- | ------------------------------------------ | ----------------------------------------------------------------- |
| **112**   | `TestReqID`   | `String`   | **yes**                                    | A unique identifier assigned by the sender to the test request.   |

For a sample message and other details, see [`FIX 4.4 : Test Request <1> message` in the FIX 4.4 documentation](https://www.onixs.biz/fix-dictionary/4.4/msgType_1_1.html).